Clamp for master sheets of printing machine



5 Jan. 17, 1956 L. F. MITCHELL CLAMP FOR MASTER SHEETS OF PRINTINGMACHINE Filed July 30, 1954 5 Sheets-Sheet l IN V EN TOR.

11262@ @ia/2,11% m4 Jan. 17, 1956 L. F. MITCHELL CLAMP FOR MASTER SHEETSOF' PRINTING MACHINE 5 Sheets-Sheet 2 Filed July 30, 1954 INVENTOR.Efffe f. /V/rc/f su,

Jan. 17, 1956 L.. F. lvm-CHELL 2,730,949

CLAMP FOR MASTER SHEETS OF PRINTING "MACHINE Filed July 50,-1954 25Sheets-Sheet 3 United States Patent CLAMP FOR MASTER SHEETS F PRINTINGMACHINE Lester F. Mitchell, Shaker Heights, hio, assignor toAddressograph-Multigraph Corporation, Cleveland, Ohio, a corporation ofDelaware Application July 30, 1954, Serial No. 446,835 9 Claims. (Cl.lill-415.1)

This application is a continuation in part of my prior application tiledJanuary 22, 1952, and assigned Serial No. 267,530, now abandoned.

This invention relates to improvements in or relating to devices forsecuring the ends of a printing plate or master sheet on the drum orcylinder of a rotary printing machine. More particularly, the inventionis concerned with the provision of a clamping device which willfacilitate rapid mounting of the leading end of a thin flexible printingplate on the drum or cylinder of a rotary printing machine and thesubsequent removal thereof without manipulation of thec lamping device.Further, the invention is concerned with the provision of an improvedclamping device which will accurately position and secure one end of athin flexible printing plate to the periphery of a printing drum withoutdamage to the plate, and in a manner which will permit the plate to bereadily removed without manipulation of the clamping device or damage tothe plate. These therefore are the general objects of the presentinvention.

A further object of the invention is to provide an improved clampingdevice for clamping one end of a thin flexible printing plate to theperiphery of a printing drum in a manner which will permit a secondnarrow printing plate to be superimposed on the first plate and held inposition by the same clamping mechanism without diturbing the positionof the previously clamped plate.

Another object of the present invention is to provide a clamp forpositioning the leading edge of a thin flexible metal or paper printingplate to the drum of a rotary printing machine by engaging theleadingedge of the plate with one or more clamping members which are yieldinglyurged into clamping position in such manner that the clamping pressureincreases as the clamps move into position and decreases as the clampsmove away from clamping position to disengage the plate.

According to the present invention there is provided a printing drumhaving an axially extending recess formed `in itsperiphery and in whichan anvil and one or more master sheet or printing plate clamping membersare mounted, each clamping member being movable to and from wedgingengagement with a master sheet inserted between the anvil and suchmembers, there being magnetic means acting to move the clamping membersindividually toward the anvil. Further according to the invention, meansare provided whereby the movement of the clamping members from the anvilis restricted to retain them in the magnetic field of the magneticmeans.

In the drawings,

Fig. 1 is a fragmentary plan view of a printing machine having aprinting drum equipped with the improved printing plate or master `sheetclamping mechanism;

Fig. 2 is a transverse section, as indicated by the lines 2-2 on Fig. l,and illustrates the printing drum and clamping mechanism in endelevation;

Fig. 3 is a sectional view, on an enlarged scale, illustrating. theclamping mechanism in position to receive a printing plate, the plane ofthe section being indicated by the line 3-3 on Fig. 1;

2,730,949 Patented Jan. 17, 1956 l CC Fig. 4 is a sectional view similarto Fig. 3 but illustrating a second printing plate about to besuperimposed upon a previously positioned plate;

Fig. 5 is a sectional detail, the plane of which is indicated by theline 5-5 on Fig. 3;

Fig. 6 is a sectional view, similar to Fig. 4, but illustrating theposition of the clamping device after the second printing plate has beeninserted;

Fig. 7 is a sectional view similar to Figs. 3, 4 and 6, illustrating theremoval of a printing plate from the clamping mechanism; and

Figs. 8, 9 and 10 are enlarged sectional details similar to Figs. 3, 4and 7 but illustrating a modified clamping device.

Referring now to the drawings, particularly Figs. 1 and 2, the improvedclamping device is illustrated as being mounted on a printing drum orcylinder 10 carried by a shaft 11 which is suitably supported by a pairof spaced frame members 12. The drum 10 may be rotated by a drivingmechanism, not shown, but which coacts with a gear 14 secured to one endof the drum. The drum 10 has an axially extending slot or recess 15formed in its periphery in which the improved clamping device ismounted.

The improved clamping device 20, as shown in Figs. l to 7 inclusive,includes an elongated channel-like support 21 which is secured to thedrum 10 within the recess 15 with its flanges upstanding to provide anupwardly facing recess 22 which extends axially of the drum adjacent tobut below the periphery thereof. An anvil 23 comprising an elongated barextends axially of the drum and is secured to the upstanding flange 25of the support which lies adjacent the surface 24 of the drum recess.The upper surface of the flange 25 provides a bridging surface betweenthe periphery of the drum and the upper surface 26 of the anvil. Theanvil surface 26 recedes from the periphery of the drum and terminatesin an inwardly curved surface 27 extending axially relative to the drum.

A plurality of individually axially spaced C-shaped clamping members 30are pivotally mounted on the anvil 23. One end of each member 30provides a clamping surface 31. As illustrated in Fig. 5, the undersideof the anvil 23 is provided with a plurality of longitudinally spacednarrow clamp receiving slots 34 into which the other ends 35 of theclamping members 30 extend respectively. A bar or rod 33 extends throughthe anvil and the clamping members to provide an individual pivotalconnection therebetween.

The pivot 33 is located relative to the axis of the curvature of theanvil surface 27 so that the swinging movement of each clamping member30 about its pivot in a clockwise direction (Fig. 3) moves its clampingsurface 31 away from the anvil surface 27 while movement in acounterclockwise direction moves such surface 31 into wedging engagementwith the anvil surface 27. The movement of the clamping members 30 awayfrom the curved surface 27 of the anvil is limited by contact of suchmembers with the support 21.

The clamping members 30, at all times, are yieldingly urged in aclamping or wedging direction, relative to the anvil 23, by a series ofpermanent magnets 40. Accordingly, the support 21 and the anvil 23 aremade of nonmagnetic materials, that is materials either not noticeablyattracted by magnetism or weakly attracted thereby, while the clampingmembers 30 are made of a magnetic material, that is, a material capableof being attracted by' a magnet.

In the form illustrated in Figs. 3 to` 7 inclusive, a mag.- net 40 isprovided for each clamping member 30; These t magnets compriserelatively small cylindrical bars of lugs of a -material which whenmagnetized will have a high coercive force such as Alnicof These magnetsare mounted in suitable recesses formed in the anvil 23 and are retainedtherein by frictional engagement with the recess walls. The magnets 40are positioned so that one end `of each magnet faces .the web portion 37of a respective clamping member 30. The magnets are of such strength asto readily move their respective clamping members into a wedgingposition with the anvil surface 27er with a printing plate positionedthereon. As heretofore mentioned, the `movement of the clamping members30 away from the anvil is restricted by their engagement with thesupport 21. This movement is so related to the strength .of the magnetas to maintain the clamping members in the magnetic field of theirrespective magnets.

To facilitate the positioning of la printing plate in the clamp, the endsurface 39 of the clamping end 3i of each member 30 is beveled toprovide a surface which forms an acute angle with the surface of theanvil. This angle provides an entrance angle or throat 41 to receive theleading end of a printing plate. As shown in Fig. 3 a printing plate Ais placed with the leading end thereof in the entrance angle or throat41 formed between the surfaces 39 of the clamping members 30 and anvilsurface 27. The clamping members are then moved rearwardly, swinging ina clockwise direction about their pivots against the action of theirrespective magnets, merelyy by moving the sheet or printing plate in thedirection of the arrow of Fig. 3. The plate A is moved in the directionof the arrow in Fig. 3 until its leading edge strikes the webs 37 ofythe clamping members, which webs form a stop for the printing plate. Theplate then is drawn in the opposite direction. This movement of theplate is followed by the clamps 30 which are constantly drawn intowedging engagement with the plate, now atop the anvil, by the attractionof their respective magnets 40. This causes the clamping members towedge the plate A tightly against the anvil and prevent its withdrawal.

:If desired, the opposite or trailing end of the printing plate may besecured to the drum by any suitable tensioning device. As indicated inthe drawings the drum is provided with a series of spaced slots S0 whichextend into the 'wall of the drum adjacent the side of the drum recesswhich lies opposite the clamp, and across which the trailing edge of theprinting plate is positioned. The

Vplate is held against the surfaces 51 of the drum between the recesses50 by a series. of pins 52 mounted in an axially extending bar 53, theends of which are provided with extensions 54. Each extension 54 isprovided with a slotted opening 5S (Fig. 2) to receive a respective pinS6 which extends axially from the opposite end of the drum. Suitablesprings 57 interposed between the bar 53 and the drum 10 retain the barin position adjacent the drum Vsurface and at the same time draw itinwardly, whereby the pins 52, which have been forced through thetrailing end of the printing plate, draw the'plate tightly across thedrum surface and maintain it tensioned.

If desired, a slotted guide 59 may be provided to guide the printingplate into the throat 41 formed between the clamping members and theanvil 23. This guide 59 may be secured to the frame members 12 to extendparallel with the axis of the drum with its inner end spaced from theperiphery thereof. This member is positioned to guide the .printing.plateA into the bite of thel anvil y23 and clamping lingers 30 when asuitable indicator mark on the drum has been aligned with a similar markon the frame.

When it is desired to remove the plate from the drum, the trailing endof the plate is released by raising the trailing end clamping bar 53from engagef ment with the plate. For this purpose the operator grasps asuitable arm 58 and moves the bar 53 outward against the action of itssprings '51, thus freeing `that end of the plate. The operator thengrasps .the `free end of the plate, turns the drum in acounter-clockwise direction, and strips the plate from the drum. As thedrum is so turned the plate itself swings the clamping lingers 30 abouttheir pivots, thus releasing the wedging action between the fingers andthe anvil and permit the plate to be readily withdrawn from the clamp.

As heretofore mentioned it is preferred that a series of individuallymovable, spaced clamping members 30 be used. Accordingly, when the plateA has been clamped to the drum, a narrow plate B may be positioned tooveriie portions of the plate A by inserting one end of the plate Bbetween the plate A and certain of the clamping members, as for instancethe clamping members 30a. This is accomplished without disturbing theother clamping members which maintain the position of the main plate A.This facilitates the use of supplemental master plates to supply data inaddition to that on the main plate. Likewise, the supplemental plate maybe blank so that it may be used to eliminate part of the data on themain plate A. The supplemental plate B is inserted and removed in thesame manner as heretofore described in connection with the main plate A.

It is to be noted that when the clamping members 30 are moved in a platereleasing direction they move away from their respective magnets 40.Accordingly the forces acting on the clamping members 30 decreases asVsuch members are moved in a plate releasing direction. This is animportant feature of this invention as it permits a thin paper or metalfoil printing plate to be removed from the clamp without requiring anymanipulation of the clamp other than that imparted to itl by the plate.This introduction and removal of the printing plate 'is accomplishedquickly and without damage to the plate. These are important advantagesin instances where a small number of copies are to be made of each of anum ber of printing plates. In such 'instances it is often customary toomit the use of a clamp for the trailing .end of the plate, which,combined with the use of the clamp of this invention enables theprinting plates to be changed in a minimum length of time.

Figs. 8, 9 and 10 illustrate a modified form of the invention. This formis similar in many respects to that heretofore described. Accordingly,the same references Will be given similar or identical parts. In Vthismodified form the anvil 23 is formed of sheet metal and is secured to asupport 60, which in this instance, comprises a relatively thin metallicplate. The support 60 is secured to the wall 24 of the drum recess 15 asby bolts 61.

The clamping members 62,`like the members 30 heretofore described,comprise a series of C-shaped members which are individually pivoted ona rod 33 carried by the anvil 23. These clamping members are yieldinglyurged into their clamping positions by a series of individual magnets40a. The magnets 40a are mounted Yin an `elongated bar of non-magneticmaterial 63 which is the anvil 23, the magnets 40a just overlay theedges of Y their respective magnets. As the members 62 are moved totheir open positions, shown in Fig. lO, the lower `ends of the legs 64thereof swing across the tops of the magnets toward the support 60 sothat they overlay the bar 63. These legs 64 abut the support before theyleave the field of force of their respective magnets 40a.

The modified form, like that first described, is so arranged that .theeilect of the magnets on their respective clamping members decreases asthe 'clamping members move from a clamping to an open position, andincreases as they return to their clamping positions. The modified formpermits the use of comparatively strong magnets and so positions themthat the printing plates cannot project between the magnets and theirclamps when being introduced into the clamps thereby avoiding anypossible interference thereby with the clamping forces. Further themodied form permits the magnets to be mounted closer to axis of theprinting cylinder to which the clamp is applied and thereby minimizesthe centrifugal force of the rotating cylinder.

From the foregoing it will be seen that the present invention provides asimple and eflicient device for clamping the leading end of a printingplate to a printing drum, and which device is readily applied to thedrum of a rotary printing machine. The movable members of the deviceareso positioned that the centrifugal force developed by the rotation ofthe drum acts to bring the clamping member to a closed position.Further, the arrangement is such that a relatively small force isrequired to move the members to clamping position and such forcedecreases as the clamping members move to an open position therebyavoiding possible damage to the plate even when the printing plate isinserted and removed from the clamping device without manipulation ofthe device other than by the plate itself.

I claim:

1. A clamping device for securing a thin flexible printing plate on theperiphery of a printing machine cylinder having an axially extendingrecess formed in its peripheral surface, said device comprising asupport mounted in said recess and made of a non-magnetic material, saidsupport having a surface on which one end of a printing plate may bepositioned, a plate clamping member mounted in said recess for movementto and from wedging engagement with said surface whereby a printingplate positioned thereon may be wedgingly held in position on saidsurface by said clamping member, a second member carried by said supportand coacting with said Iirst named member to constantly tend toyieldingly move said clamping member toward a wcdging position, one ofsaid members being a permanent magnet, the other of said members beingformed of a material magnetically attractable relative to the magnet andwherein said members are positioned relative to each other and to saidsurface to cause the force of the magnetic attraction to increase as theclamping member moves toward wedging position and to decrease as theclamping member moves from wedging position.

2. A clamping device according to claim 1 in which the second namedmember is a permanent magnet and is tixed relative to said support.

3. A clamping device according to claim 1 having a row of axially spacedindividually movable clamping members.

4. A clamping device according to claim 3 in which the clamping membersare made of a magnetically attractable material and there is anindividual permanent magnet for each clamping member.

5. A clamping device according to claim 4 wherein each clamping memberhas a surface extending at an acute angle from its contact with the saidsupport surface to provide a bite or entrance angle into which the endof a printing plate may be moved and wherein continued movement of theprinting plate may cause the plate to move the clamping members awayfrom the clamping position and wherein the forces opposing such movementdecrease with opening movement of the clamp.

6. A clamping device for securing one end of a thin flexible printingplate on a rotary printing drum having an axially extending recessformed in its periphery, said device comprising an axially extendinganvil mounted in said recess and made of a non-magnetic material, saidanvil having a printing plate supporting surface and a series of axiallyspaced inwardly facing transverse slots, a series of spaced cylindricalmagnets mounted in said anvil above and parallel with respective slots,a plurality of C-shaped clamping members, each member having one endextending into a respective slot and pivotally connected to the anvilfor movement in a plane parallel with the slot, each member extendingoutwardly and upwardly from the slot across the path of magnetic ux ofthe respective magnet and having its other end overlaying the end of aprinting plate positioned on said anvil surface, said members being madeof a .magnetic material whereby the magnets act to yieldingly urge theminto contact with such printing plate, non-magnetic means to limit themovement of the members away from the anvil, and wherein the last-namedend of each clamping member has a surface forming an acute angle withthe upper surface of the anvil to provide a bite to receive a printingplate.

7. A clamping device for securing one end of a thin iiexible printingplate to the drum of a rotary printing machine having an axiallyextending recess in its periphery, said clamping device comprising anaxially extending anvil mounted in said recess and made of non-magneticmaterial, said anvil having an outwardly facing printing platesupporting surface having a free edge projecting into said recess, aplurality of axially aligned C-shaped clamping members having lower armportions pivotally connected beneath said anvil for independent pivotalmovement about an axially extending axis relative to said drum, saidmembers being made or" a magnetic material and extending from theirpivots around the: free edge of said anvil and having upper arm portionsoverlaying said plate supporting surface and movable to and from wedgingengagement with the end of a printing plate supported by such surface,each of said clamping members having a downwardly extending legprojecting toward the axis of said drum, a support of non-magneticmaterial secured to said drum within said recess and spaced below saidlegs, a plurality of permanent magnets mounted in said support withtheir magnetic axes extending substantially radially relative to saiddrum, said magnets being so positioned relative said clamp legs that thelatter swing substantially across one pole of a respective magnet asthey rock about their pivots and to cause the magnetic force to act atall times to rock said members into clamping position, and wherein theforce of said magnets acting on said members increases as the membersmove into c1amping position and decreases as said members are moved awayfrom clamping position.

8. A clamping device according to claim 4 wherein said support has anarcuate plate supporting surface and cach clamping member comprises anindividual C-shaped member made of magnetically attractable material oneend of which is pivotally connected with the support below said surfaceand the other end of which projects above said surface and is adapted tocontact a printing plate on said surface, and wherein said magnetscomprise cylindrical members and are mounted in said support with oneend projecting toward a portion of its respective clamping memberintermediate the ends thereof.

9. A printing plate clamping device according to claim 8 having means tolimit the movement of the clamping members away from the platesupporting surface of said support and retain them in the magnetic lieldof said magnets.

References Cited in the file of this patent UNITED STATES PATENTS838,512 Wagner Dec. 11, 1906 2,101,173 Gegenheimer Dec. 7, 19372,123,997 Iirousek July 19, 1938 2,213,014 Owen Aug. 27, 1940 2,231,291Morrison Feb. 11, 1941 2,309,161 Breman et al. Jan. 26, 1943 2,320,239Huck May 25, 1943 2,453,927 Morse Nov. 16, 1948 2,553,856 Janke May 22,1951

